When saving videos, most programs ask you to choose a compression type, “small, medium or large.” If you save a file at its full size/resolution, then your photos and sound will have better quality. When uploading to the Internet, it’s better to use a smaller resolution files because, though there is some reduction in quality, the file won’t take as long to upload and your viewer won’t require so much bandwidth (speed of Internet connection) to interact with the file.
If you were to burn your documentary onto a DVD to show on a DVD player or on a larger screen, you’d absolutely want to save it at as high of resolution as possible to improve the viewer experience.
There is always a tension between high quality and smaller file sizes when working with Internet media. We are forced to make compromises to create a balance between quality and end-user interaction.